The rise of antimicrobial-resistant pathogens has driven efforts to discover novel effective antimicrobials from natural sources such as bee products. Honey has established clinical usage thanks to extensive research around its antimicrobial properties. The main mechanism of action of most non-Manuka honeys is the conversion of glucose into H2O2 and gluconic acid by bee-derived glucose oxidase. Another bee product with potential therapeutic applications is propolis, a mixtures of plant resin and beeswax. Its proposed main bioactive components are plant-associated phenolic compounds. Most research in this area has focused on Apis mellifera, with far fewer studies examining other bee species such as Tetragonula carbonaria. Studies examining T. carbonaria honey and propolis have reported species-specific activity against certain bacterial species, however, they have not been tested against a wide panel of bacteria and fungi.
We examined the antimicrobial activity of paired honey and propolis samples from eight T. carbonaria hives in the New South Wales (NSW) region. We tested the samples against a diverse range of microbes, including seven bacteria and eight fungi. Honey samples were tested directly and propolis samples were made into ethanolic extracts. Honey samples showed species specific activity; all samples were active against Staphylococcus aureus, Enterococcus faecalis, Streptococcus pyogenes, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella enterica, Microsporum canis, and Trichophyton interdigitale, some were active against Cryptococcus neoformans, and Rhizopus oryzae, and none were active against Candida glabrata, Candida albicans, Aspergillus flavus, and Aspergillus fumigatus. H2O2 concentration was determined using commercially available peroxide test strips and did not correlate with antimicrobial activity, suggesting that the mechanism of action extends beyond solely H2O2. Looking at propolis, we found it behaved distinctly different from honey. All propolis sample were exclusively active against S. aureus, E. faecalis, E. coli, R. oryzae, M. canis, and T. interdigitale. The spectrum of activity observed was different to that observed from Queensland propolis in previous studies, suggesting that NSW propolis may contain distinct active compounds. Overall, we show that T. carbonaria honey and propolis from NSW are highly active against specific microbial species and are promising candidates for developing into antimicrobial agents.